[WestieJeff]

It's true the pool stores often suggest this, but they like to give out terrible information. Their first priority seems to be selling a person as many chemicals as they will buy. The TDS will increase from water evaporation, but it needs to get extremely high before it has any affect on the pool itself.

I find the reason that pool stores recommend a drain is most people chlorinate with tablets or granular chlorine which includes CYA/stabilizer (all solid forms of chlorine have CYA/stabilizer included). CYA/stabilizer never leaves your pool once you put it in, unless you drain it. It doesn't break down or "use up" over time. The more CYA/stabilizer in your pool, the less effective the chlorine is at killing things and you have to use more chlorine. Once CYA/stabilizer is too high, there is practically no way to add enough chlorine to make it effective.

Anyways, if a person doesn't use chlorine tablets/granular because they are on a salt system or use liquid chlorine then there is no need to drain regularly. I'm on year 3 or 4 from my pool fill and it's fine. I'm sure it will be 5+ years before I need to drain and fill.

Originally Posted by NLVgal

Also, what no one at the new pool place will tell you is that they recommend you drain the pool every year or so and fill it with fresh water because the build up of the salts and other chemicals makes the water "dead".

I know that's a ridiculous term, but I've heard the same thing from many people. It essentially means that the water evaporates, but the salts that result from the breakdown of the chlorine do not, so it requires draining the pool, even though you are constantly refilling it.

[AA702]

Originally Posted by WestieJeff

It's true the pool stores often suggest this, but they like to give out terrible information. Their first priority seems to be selling a person as many chemicals as they will buy. The TDS will increase from water evaporation, but it needs to get extremely high before it has any affect on the pool itself.

I find the reason that pool stores recommend a drain is most people chlorinate with tablets or granular chlorine which includes CYA/stabilizer (all solid forms of chlorine have CYA/stabilizer included). CYA/stabilizer never leaves your pool once you put it in, unless you drain it. It doesn't break down or "use up" over time. The more CYA/stabilizer in your pool, the less effective the chlorine is at killing things and you have to use more chlorine. Once CYA/stabilizer is too high, there is practically no way to add enough chlorine to make it effective.

Anyways, if a person doesn't use chlorine tablets/granular because they are on a salt system or use liquid chlorine then there is no need to drain regularly. I'm on year 3 or 4 from my pool fill and it's fine. I'm sure it will be 5+ years before I need to drain and fill.

* Just to correct on what you said Cal-Hypo does not contain CYA, and comes in power form or tablet form. Chlorine gas is also used in some cases and does not contain CYA (There are some guys who use this to this day). There is also another one called Lithium Hypo Chlor that doesn't contain any CYA. Some pools that are equipped with a backwash valve because they have a D.E. filter or Sand will also have no problem with using anything with CYA because you can gradually take water out of the system and reduce your CYA on a regular basis. Adding a backwash valve can do wonders.

I know someone who actually has machine that reduces CYA and hardness and is used for those people who do not want to drain on a regular basis. I'm not sure what the technology consists of but he has had good results in Austin Tx.

[lvoc]

My pool water is around 8 years old. And it is fine. Now my pool is covered and I generally use nothing other than liquid...though I do throw tablets in the system for the winter.